msvcmaker: Fix msvc project file generation under MinGW32.

When converting a makefile to a msvc .dsp file, if a line is ended with
a back slash, it will be joined with next line. This patch changes the
joining character from '\n' to a space in order to fix the bug of 
running MinGW32 on Windows.

tools/winapi/msvcmaker

@@ -135,7 +135,7 @@ MAKEFILE_IN: foreach my $makefile_in_file (@makefile_in_files) {
 	    chomp $line;
 	    if($lookahead) {
 		$lookahead = 0;
-		$_ .= "\n" . $line;
+		$_ .= " " . $line;
 	    } else {
 		$_ = $line;
 	    }